Cyclophanes containing large polycyclic aromatic hydrocarbons

Abstract

Cyclophanes have been firmly entrenched as a distinct class of compounds for well over half a century. The two main factors that have kept this field of chemistry going so strongly for such a long time are tremendous structural diversity and the interesting behaviour that is often observed. Although a very large number cyclophanes has been reported, only a very small proportion of them contain polycyclic aromatic systems that can be thought of as "large", i.e. with ≥4 rings. This Review puts the spotlight on such cyclophanes, illuminating both the chemistry that was used to synthesize them and what was learned from studying them. Context for the main body is provided by the careful consideration of the anatomy of a cyclophane and the classification of general synthetic approaches. The subsequent sections cover eleven different PAHs and are organized primarily according to increasing size of the aromatic system, starting with pyrene (C16, the only large polycyclic aromatic system to have been incorporated into numerous cyclophanes) and ending with hexabenzo[bc,ef,hi,kl,no,qr]coronene (C42).

Dibenzo[a,e]pentalenophanes: Bending a Non‐Alternant Hydrocarbon

“…In addition, these results show that the DBP‐phane framework possesses a degree of flexibility, which allows for different conformations to be energetically viable. For (2,7)pyrenophanes, Bodwell and co‐workers found bend angles for the central pyrene unit between 34.6° and 109.2°, depending on the cyclophane size …”

“…Cyclophanes are rings, built up of mancude‐ring systems (or assemblies thereof) alternating with (un)saturated chains . Of the large number of reported cyclophanes, however, only few contain polycyclic aromatic hydrocarbons (PAHs) consisting of at least four annulated rings . Examples of such incorporated PAHs are pyrene, corannulene, acenes, teropyrene, and hexabenzocoronene .…”

“…In the synthesis of such cyclophanes, one of the biggest challenges is to introduce strain through bending of the preferentially planar π‐system. Several strategies have been used, of which the most successful ones leading to highly strained PAH‐cyclophanes involve the synthesis of a bridged PAH‐precursor . This relatively unstrained species is then converted to the PAH, usually in the last synthetic step, whereby the obtained aromatic stabilization energy can counterbalance the strain energy (Scheme ).…”

Luminescent Carbon Dot Mimics Assembled on DNA

“…16 While cyclophane skeletons have been exploited to organize polyaromatic hydrocarbons in stacks, they are synthetically challenging and have been structurally limited to two layers. 17 …”

Ein Zugang zum enantiomerenreinen axial chiralen Cyclophan Isoplagiochin D durch atrop‐diastereoselektive Heck‐Kupplung

“…[1] Betrachtet man die Synthese dieser faszinierenden Klasse von Makrocyclen, so ist die Cyclisierung die große Herausforderung.I nsbesondere fürkleine Cyclophane ergibt sich durch die Rigidität der gebildeten Ringstruktur ein erhçhter Syntheseanspruch. [1] Betrachtet man die Synthese dieser faszinierenden Klasse von Makrocyclen, so ist die Cyclisierung die große Herausforderung.I nsbesondere fürkleine Cyclophane ergibt sich durch die Rigidität der gebildeten Ringstruktur ein erhçhter Syntheseanspruch.…”